This invention relates to an electrophotographic printing machine, and more particularly concerns an improved cleaning system for use therein.
In electrophotographic printing, a charge retentive surface such as a photoconductive member is charged to a uniform potential. The uniformly charged photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the sensitized photoconductive surface discharges the charge selectively. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document being reproduced.
It should be understood that for the purposes of the present invention, which relates to the removal of residual toner particles from a charge retentive surface subsequent to image transfer, the latent electrostatic image may be formed by means other than by the exposure of an electrostatically charged photosensitive member to a light image of an original document. For example, the latent electrostatic image may be generated from information electronically stored or generated in digital form which may afterwards be converted to alphanumeric images by image generation electronics and optics. For example, the latent image can be formed electronically by using a modulated laser used in connection with a suitable scanning device. However, such image generation electronic and optic devices form no part of the present invention.
Development of the electrostatic latent image recorded on the photoconductive surface is achieved by presenting developer material to the latent image. Typical developer materials comprise a heat settable plastic powder, known in the art as toner particles. The toner particles are selected to have the appropriate charge relative to the electrostatic latent image recorded on the photoconductive surface so that they are electrostatically attracted to the latent image.
After development of the latent image to render it visible, the powder images are transferred to a copy substrate such as plain paper.
Frequently, residual toner particles remain adhering to the photoconductive surface after transfer from the photoconductive surface to the substrate material. Heretofore, cleaning devices such as webs, brushes or foam rollers, have not been entirely satisfactory in removing residual toner particles from the photoconductive surface in all instances.
One of the more attractive methods for removing residual toner particles from the photoconductive surface has been to use a rotating magnet enclosed in a stationary, non-magnetic shell or, alternatively, to utilize stationary magnets enclosed within a rotating, non-magnetic shell. This system attracts carrier granules which, in turn, attract the residual toner particles from the photoconductive surface thereto. However, cleaning systems of this type are presently rather costly and complex in order to achieve the desired cleaning efficiency.
Another of the more attractive methods of removing residual toner particles from a charge retentive surface is to use a blade to either wipe and/or chisel the residual toner from the surface.
Cleaning blade structures are commercially used for removing residual toner from drum-type photoreceptors used in machines that have a relatively slow (i.e., a small number of copies produced in a given time period) process speed. However, their use in the higher speed machines and in conjunction with belt-type photoreceptors has not met with great success.
Previous blade cleaning has employed urethane blades with edges capable of conforming to surface of the photoreceptor drum. The problems with such an arrangement include excessive blade wear, (particularly at higher operating speeds) need for lubricant, blade tucking and toner powder clouding. Low contact pressure solves the problem of blade wear but results in inefficient cleaning.
In view of the foregoing, it can be seen that a highly efficient, long life blade cleaning apparatus for removing residual toner from a photoreceptor surface is desirable.